The present invention relates generally to the field of friction measuring, or testing, and in particular to a method and apparatus for measuring the static and dynamic coefficients of friction of a surface. The method and apparatus also find use in measuring or testing the quality of lubricants.
Friction measuring devices are known to the prior art. They generally operate by developing linear forces between the surface under test and a bearing pad. The force necessary to move the bearing pad relative to the test surface is utilized to determine the coefficient of friction.
While these known devices are, to some extent, useful in developing information about static coefficient of friction, they are substantially useless insofar as tracing dynamic characteristics. These devices also tend to be somewhat inaccurate when measuring static coefficient of friction, because this characteristic is determined at a time when there is an abrupt breakaway of the friction pad from the test surface. Furthermore, the known devices are generally bulky and heavy, detracting from portability, and are sensitive to misalignments and surface irregularities.
The present invention is directed to an advanced method and apparatus for measuring or testing static and dynamic coefficient of friction, which overcome each of the disadvantages and drawbacks of known prior art techniques.